Understanding Inverters in Off-Grid Energy Applications
Here at Wibuy, we understand that inverters can be confusing. There is allot of information out there and most of us don't have backgrounds in solar system installation. In this article, we will cover some of the basics and different types of a typical inverter. We'll give you some information to help select the inverter that's right for your application.
Understanding the Basics
WATTS- Everyone has heard this before but its meaning isn't usually understood. Watts are an electrical measurement. Watts are just how much power a device is using or producing. The wattage of something always stays the same. It is calculated by the voltage of something multiplied by its amperage. So if a device is consuming 10 amps at 120 volts, then that device is using 1200 Watts.
AMPS- Amps are a measure of the electrical running through something in one moment. They are a very important unit of measure for safely connecting electrical components. They determine the size wire that you will need for your system ( Especially on the battery side of the inverter ) Too small of a wire and they will get hot, and that is never a good thing.... This can be very dangerous, so make sure you know your amps.
WATT HOURS- Watt Hours are simply how many watts you are using per hour. Remember that the Wattage of a device never changes. A 50 watt device is always a 50 watt Device. But if a 50 watt device is on for 10 hours, then you now have 500 Watt-Hours. ( 50 watts consumed per hour for 10 consecutive hours ). You multiply the wattage of your load by how many hours it will be running to get your Watt-Hours. Most Off-Grid system components are labeled in Kilo-watt Hours. 1 kWh is just 1000 watt hours.
Amp Hours- An amp hour is basically the same thing but for amperage instead of wattage. Amp hours are important because this is how your battery capacity is typically measured. You don't wanna mess that up...
What Size Inverter Do You Need??
All inverters have a continuous rating and a surge rating. These two factors are your most general way of deciding which inverter you need for your application. Take the time to completely understand these two measurements and double check the wattage of the loads you will be running before choosing an inverter.
Surge Power- This is the maximum power that an inverter can push and it is usually only for a short amount of time ( this is typically only a few seconds to a couple minutes ). This means that the inverter will handle an overload of that many watts for the specified amount of time. Surge capacity will differ greatly between different inverters. Allot of your electrical loads with motors or pumps (refrigerators etc.) require much more energy when they turn on then they take to run after they have been turned on. This is where your inverters surge power rating comes into play. Generally, a 3 to 15-second surge rating is enough to cover 99% of all appliances but always check to be sure, They can be pricey.
Continual Power- This is what Your inverter has to supply on a regular basis. This is the power that all everything running at once consumes. The continual power is a steady flow of power that is supplied to all of your appliances when they are running.
General Information- The inverters with the lowest surge ratings are the high-speed electronic switching type which are the most common these days. These usually produce 25% to 50% maximum overload. These inverters are usually between 50 to 5000 watts. The highest surge ratings are the transformer based, low-frequency switchers. Surge ratings on these can range up to 300% for short periods. While high-frequency switching allows a much smaller and lighter unit, due to the much smaller transformers used it also reduces the surge or peak capacity. Although the high-frequency switching type doesn't have the surge capacity of the transformer based, they do have some definite advantages. They are much lighter, usually quite a bit smaller, and they are much cheaper. However, if you are going to run something like a submersible well pump, you will need either very high surge capacity or you will need to oversize the inverter above its typical usage, so that even at maximum surge the inverter will not exceed its surge rating.
What Kind Of Inverters Are There
Sine Wave- The major advantage of a sine wave (Pure Wave) inverter is that all of the equipment which is sold on the market is designed for a sine wave. This guarantees that the equipment will work to its full specifications. Some appliances, such as motors and microwave ovens will only produce full output with sine wave power. A few appliances, such as bread makers, light dimmers, and some battery chargers require a sine wave to work at all. Sine wave inverters are always more expensive - from 2 to 3 times as much.
Modified Sine Wave- A modified sine wave inverter will work fine with most equipment, although the efficiency or power will be reduced with some types of equipment such as motors, pumps, fans etc which will use about 20% more power from the inverter on average. This is because a part of the modified sine wave itself is a higher frequency while a pure sine wave operates at 60 Hz. Some fluorescent lights will not operate quite as bright, and some may humm or buzz. Appliances with electronic timers and/or digital clocks will often not operate correctly because they use a regular sine wave to measure time. Items such as bread makers and light dimmers may not work at all - in many cases appliances that use electronic temperature controls will not control. things like variable speed drills will only have two speeds - on and off.
I hope this helps clear up some of the confusion around the inverter.
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- Joshua Powers